import re
def isPythonID(name):
    pattern='^[a-zA-Z_][a-zA-Z0-9_]*$'
    match=re.search(pattern,name)
    if match is None:
        print('%s is not ID'%name)
    else:
        print('%s is ID'%name)
isPythonID('abc')
isPythonID('Abc_123')
isPythonID('123')
